It is becoming increasingly clear that emerging mobile devices such as handsets, mobile internet devices (MIDs), palmtops, and laptops will support multiple wireless technologies to achieve high data rates and provide ubiquitous connectivity. These mobile devices will include WiFi, Bluetooth (BT), global positioning system (GPS), cellular second generation (2G), and third generation (3G) technologies, such as global systems mobile (GSM), universal mobile telecommunications system (UMTS), and emerging fourth generation (4G) technologies such as mobile WiMAX (worldwide interoperability for microwave access) and/or LTE (long-term evolution).
From a user perspective, multi-radio devices extend the flexibility to choose among available accesses and services according to different needs, such as quality of service (QoS), cost, and so on, as well as the freedom to access any network that is available.
From an operator perspective, deploying a mix of multiple access systems at various stages in time and subject to market and regulatory considerations may improve the availability, reliability, and capacity of the services offered to the end users.
Multiple access systems should interact seamlessly for the users to receive a variety of content via a choice of delivery mechanisms, depending upon the particular terminal capabilities, location, and user profile. Multiple radios also must work together on the same device. For a multi-radio device, the minimum requirement is the seamless handoff, i.e., users may seamlessly switch their service from one radio to the other without impacting their service. There are also scenarios in which multiple radios are expected to operate simultaneously to provide multi-media service.
Current radio access technologies have independent physical (PHY) layer and MAC layer (where MAC is short for media access control) operation and use client-based mobile Internet protocol (IP), which requires a complex protocol stack in the mobile device and on the network side. It is very challenging to support either seamless handoff or simultaneous multi-radio operation under the current situation for several reasons: 1) because of the close proximity of the radio frequencies, active radios may interfere with each other; 2) the radio frequency (RF) module is shared between two or more wireless technologies; 3) the physical interface to the platform is shared by two or more wireless technologies (e.g., there exists a power drain limitation).
Thus, there is a continuing need for an architecture that overcomes the shortcomings of the prior art.